I started my opening preparation only when I joined a chess club. My first opening book was The Batsford Chess Openings book 2 which has many different openings in it well explained by well renowned British Chess Author GM Raymond Keene. I saw all the mounds of theory with the 1 d4(Queens Pawn Opening) and 1 e4(Kings Pawn Opening) and decided as White to play something with less theory. I immediately hit upon the idea of playing the Reti opening i.e. 1 Nf3 and I got good results with it. 
As Black I played the Caro-Kann (1 e4 c6) and the Slav (1 d4 d5 2 c4 c6) basing my strategies around a quick c6 move. Now as White I found that after 1 Nf3 d5 2 c4 d4 I got a cramped position so after a period of a few years playing it I decided to move on to experiment with 1 g3 (The Benko-Larsen Opening), the Kings Indian Attack i.e.(1 g3 2 Bg2 3 Nf3 or 3 c4) and then read up on playing 1 d4 d5 2 Nc3 Nf6 3 Bg5 (The Veresov Opening) but it wasn't until I decided to look at 1 c4 (The English Opening) that I found a permanent Opening system, which I have stuck with so far, for 24 years. I am writing a book on my opening repertoire which will be published as web pages on this site. I am still working on it but it can be seen below:-
  1. The English Opening

  2. The Alekhine Defence

  3. The Pirc Defence

  4. The Grunfeld Defence

  5. The King's Indian Defence

  6. The Queen's Gambit Accepted

  7. The Sicilian Dragon

I found also their was a reason why, as Black, c6 isnt played  early and that is because it hampers Blacks Light Squared Bishop and I found I was loosing or drawing games which I shouldn't with these openings. I then decided to play as Black a system based around a Fianchettoed Bishop on the King side i.e. I played The Modern (1 e4 g6), The Pirc (1 e4 g6 2 d4 Bg7 3 Nc3 Nf6) and the Kings Indian Defence (1 d4 g6 2 c4 Bg7 3 e4 d6 4 Nc3 Nf6). Although I got good results with this system of development I finally decided to play after around 3 years of that system, The Alekhine Opening (1 e4 Nf6) this is very provocative, another provocative opening I decided to play, in 1998, against 1 d4 was The Grunfeld Defence (1 d4 Nf6 2 c4 g6 3 Nc3 d5).
I still play both openings today but have included a few openings to play against lower graded opponents which are less theoretical like The Queens Gambit Accepted (1 d4 d5 2 c4 dc) and the unusual Dunst Opening (1 Nc3) . I also have learnt and am going to learn about the Sicilian Dragon, which is highly theoretical.   Actually the very latest development in my play is the throwing out of my Fritz Trainer Opening Prep for some very expensive training from an expert trainer International Master Alex Battey.  He has given me specific lines i have learnt for specific games.